The primary purpose of this study is to examine the regulation of translation in mouse plasma cell tumors synthesizing immunoglobulin light chains. The light chain mRNA has been isolated from one such tumor (RPC-20) and the factors controlling the translation of this mRNA will be studied in several cell-free systems. In addition, isoaccepting tRNA's for the amino acid serine have been partially purified from the RPC-20 tumor, and the effects of these isoacceptors on the translation of the RPC-20 light chain mRNA will be studied. Other projects to be undertaken will involve: (a) attempts to isolate a high molecular weight nuclear RNA precursor of light chain mRNA and to observe its translation under cell-free conditions; (b) a study of the possible regulation of immunoglobulin biosynthesis by tRNA in cell-free systems. In addition, a study of the regulation of translation and transcription in Streptomyces antibioticus, the bacterium which produces actinomycin, will be undertaken. Bibliographic references: Jones, G.H. (1975), "Ribonucleic synthesis in Streptomyces antibioticus: Stable ribonucleic acid species synthesized by young and old cells," Biochem. Biophys, Res. Commun. 63, 469-475. Rogers, P.A., Jones, G.H., and Faulkner, J.A. (1975), "Changes in protein synthetic activity in skeletal muscle subjected to acute exercise stress." Medicine and Science in Sports, 7, 66.